1. Field of the Invention
The present invention is related to an Al--Mg series aluminum alloy rolled sheet, which is used for producing formed articles, such as a body sheet, air-cleaner, oil tank, and the like of an automobile, in which a high strength and formability, particularly the elongation, bulging, and bending properties, are required. The present invention is also related to a method for producing the Al--Mg series aluminum alloy rolled sheet.
2. Description of the Related Art
The most frequently used sheets for forming body sheets and the like of an automobile have heretofore been cold-rolled steel. In recent years, however, in order to decrease the weight of an automobile, and thus the fuel consumption thereof, there has been an increasing demand for conventional cold rolled steel sheets to be replaced by aluminum alloy rolled sheets. Accordingly, an aluminum alloy sheet 5052 alloy of the Al--Mg series with 0 temper, 2036 alloy of the Al-Cu series with T4 temper, and 6009 and 6010 alloys of the Al--Mg--Si series with T4 temper have been employed for the above applications.
The 5182 alloy with 0 temper exhibits excellent formability but Luder's marks occur in the forming. It also exhibits a noticeable softening at the baking after forming.
The stretcher strain free (SSF) 5182 alloy does not show Luder's marks but exhibits poor formability.
The 2036 alloy with T4 temper exhibits poor corrosion resistance and softens after baking. In addition, its formability deteriorates due to secular changes.
The 6010 and 6009 alloys with T4 temper exhibit somewhat poor corrosion resistance. In addition, its formability deteriorates due to the secular change.
Al--Mg--Zn--Cu alloy exhibits an excellent formability, but the strength-reduction due to baking is great and the formability deteriorates due to the secular change.
None of the previously known alloys satisfy all of the requirements of good formability, freedom from secular changes, nonformation of Luder's marks, a small strength decrease after baking or forming, and good corrosion resistance.